JP2016526299A - Apparatus and method for bonding substrates - Google Patents

Abstract

The present invention is a method for bonding a first substrate (3) to a second substrate (8) at the contact surfaces (3k, 8k) of both substrates (3, 8), comprising the following steps, in particular: The following sequence: the first substrate (3) is mounted on the first mount surface (2o) provided in the first mounting device (1), and the second substrate (8) is mounted on the second mount Mounting on a second mounting surface (2o ′) provided in the apparatus (4), contacting both the contact surfaces (3k, 8k) at a predetermined bonding start point (20), and the bonding The first substrate (3) is bonded to the second substrate (8) along the bonding wave that travels from the starting point (20) to the side edges (3s, 8s) of both substrates (3, 8). One with steps On. The method according to the invention bonds the first substrate (3) and / or the second substrate (8) outside the bonding start point (20) for the alignment of the contact surfaces (3k, 8k). Before and / or during bonding. The invention further relates to a corresponding device.

Description

  The invention relates to a method for bonding a first substrate to a second substrate according to claim 1 and to a corresponding apparatus according to claim 9.

  Advanced miniaturization in almost every part of microelectronics and microsystems technology leads to constant further development of all technologies and using these technologies to increase the density of all kinds of functional units on the board be able to. Such functional units belong, for example, to microcontrollers, memory components, MEMS, all types of sensors or microfluidic devices.

  In recent years, techniques for increasing the lateral density of such functional units have been significantly improved. On the contrary, in some sub-regions of microelectronics or microsystem technology, it is so advanced that further increase in the lateral density of the functional units is no longer possible. In microchip manufacturing, it is as if the maximum achievable resolution limit has already been achieved for a substrate to be manufactured by lithography. That is, due to physical or technological constraints, increasing the lateral density of functional units is no longer completely possible in just a few years. The industry has already been working on the development of 2.5D and 3D technologies for several years to address this issue. With 2.5D technology and 3D technology, the same functional unit or even different types of functional units are aligned with each other, stacked one above the other, permanently connected to each other, and wired together with corresponding conductor tracks It becomes possible to do.

  One of the key technologies for realizing such a structure is permanent bonding. “Permanent bonding” means all methods by which substrates can be bonded together such that the separation of the substrates is only possible due to high energy consumption and concomitant destruction of the substrates. There are different types of permanent bonding.

  One extremely important permanent bonding method is fusion bonding, also called “direct bonding” or “molecular bonding”. “Melting bonding” refers to the process of permanent bonding of two substrates through the formation of a covalent bond. Melt bonding occurs especially on the surface of non-metal-non-organic materials.

  Basically, it is desirable to distinguish between pre-bonding and original permanent bonding. “Pre-bonding” is a bond between both surfaces that is spontaneously formed when two surfaces contact each other, and the bond strength is higher than the bond strength of permanent bonding formed by a heat treatment performed later. Means low binding. However, the bond strength produced by prebonding is sufficient to transport both substrates without causing relative displacement of the substrates. That is, the bond strength between the two substrates can be said to be sufficient to carry the substrate stack (stack) without problems, but this bond strength can be achieved using a special device. It is low enough that a new separation without destruction can take place. This has the following important advantages: That is, after pre-bonding, the structures of both substrates can be measured and their relative position, strain and orientation can be measured. During the measurement process, if it is detected that there is misorientation of the structure and / or local (local) and / or global (global) distortion or that particles are present at the interface, The stack can again be separated accordingly and processed again. After it is confirmed that the pre-bonding has been successfully performed and there is no particular inconvenience, permanent bonding is formed by a heat treatment process. During the heat treatment process, the supply of thermal energy causes chemical and / or physical strengthening of the bonding of the surfaces of both substrates. This permanent bonding is irreversible in the sense that separation without destruction of both substrates is no longer possible. In the following, pre-bonding and permanent bonding are no longer clearly distinguished, and are generally expressed only as “bonding”.

Very popular melt bonding is performed on silicon and silicon oxide substrates. Silicon is often used as a base material for manufacturing microelectronic components, such as microchips and memories, based on its semiconductor properties. “Direct bonding” can also occur between highly polished metal surfaces. The underlying bonding properties are certainly different from those of fusion bonding, but the mechanism by which both surfaces are contacted with each other by a traveling bond wave can be explained by the same physical properties. It is also conceivable to connect two hybrid surfaces by “hybrid bonding”. “Hybrid surface” means a surface composed of two different materials. Of both materials, the first material is usually confined to a small space, while the second material surrounds the first material. For example, a metal contact is surrounded by a dielectric. When a hybrid bond is formed by bonding of two hybrid surfaces, the bonding wave is driven, inter alia, by melt bonding between the dielectrics, and the metal contacts are automatically matched by the bonding wave. Examples of dielectric and low-k materials (low dielectric constant materials) are:
● Non-silicone mainly composed of the following components ○ Polymer Polyimide Aromatic polymer Parylene PTFR
○ Aromatic carbon ● Silicon based on the following components ○ Silicate based on the following components TEOS (tetraethyl orthosilicate)
SiOF
SiOCH
Glass (borosilicate glass, aluminosilicate glass, lead silicate glass, alkali silicate glass, etc.)
○ General Si ₃ N ₄
SiC
SiC ₂
SiCN
○ Silsesquioxane HSSQ
MSSQ
One of the most significant technical problems in permanently bonding two substrates is the alignment accuracy of the functional unit between the individual substrates. The substrates can be aligned very accurately with respect to each other by alignment equipment, but substrate distortion can occur during the bonding process itself. Due to the distortions thus produced, the functional units are not necessarily properly aligned with each other at all positions. Alignment inaccuracies at specific points on the substrate can result in distortion, scaling errors, lens defects (magnification errors or reduction errors), etc. In the semiconductor industry, all of the theme areas related to such problems are included in the concept of “overlay”. A corresponding overview on this subject is described, for example, in “Fundamental Principles of Optical Lithography-The Science of Microfabrication” by Mack, Chris (publisher WILEY, 2007, reprinted 2012).

  Each functional unit is designed with a computer before the actual manufacturing process. For example, any other structure that can be manufactured using conductor tracks, microchips, MEMS, or microsystem technology is also designed in a computer aided design (CAD) program. However, when manufacturing functional units, it has been found that there is always a difference between an ideal functional unit constructed in a computer and an actual functional unit manufactured in a clean room. The differences can be attributed primarily to hardware limitations, i.e. technical engineering issues, but often to physical limitations. That is, the resolution accuracy of the structure manufactured by the photolithography process is limited by the size of the aperture of the photomask and the wavelength of the light beam used. Mask distortion is transferred directly to the photoresist. The machine's linear motor can only reach a position that can be reproduced within the specified tolerances. Thus, it is no wonder that the functional unit of the board cannot be exactly equal to the structure built in the computer. Therefore, all substrates already have a negligible departure from the ideal state prior to the bonding process. Comparing the position and / or shape of two functional units located on opposite sides of two substrates, assuming that neither substrate is distorted by the coupling process, it is generally already It can be seen that there is an incomplete alignment of units. This is because these functional units deviate from the ideal computer model due to the errors described above. An extremely frequent error is shown in FIG. 8 (http://commons.wikimedia.org/wiki/File:Overlaytypical model terms DE.svg. 24.05.2013 and Mack, Chris. Fundamental Principles of Optical Lithography- the Science of Microfabrication. Chichester: WILEY, p.312, 2007, a copy from Reprint 2012). As shown in the drawings, overlay errors can be roughly divided into global overlay errors and local overlay errors, or symmetric and asymmetric overlay errors. The global overlay error is uniform and is therefore independent of location. A global overlay error causes the same deviation between two functional units located opposite each other, regardless of position. Classical global overlay errors are errors I. and II. Caused by translation or rotation of the two substrates relative to each other. The translation or rotation of both substrates generates corresponding translational or rotational errors on the substrate for all functional units located opposite each other. Local overlay errors occur in relation to location and are mainly caused by elastic and / or plastic problems, and in this case, in particular, elastic and / or plastic problems caused by continuously propagating bonding waves. Caused by. Of the overlay errors shown, errors III. And IV., Among others, are referred to as “run-out” errors. This run-out error is caused in particular by distortion of at least one substrate during the bonding process. Due to the distortion of the at least one substrate, the functional unit of the first substrate is also distorted with respect to the functional unit of the second substrate. However, errors I. and II. Can also be caused by the bonding process, but are often significantly superimposed by errors III. And IV. Therefore, errors I. and II. It becomes difficult.

  In the known prior art, there are already facilities that can at least partially reduce local distortions. This is a local distortion correction by the use of active control elements (WO 2012/083978).

  In the known prior art, there is a first solution for correcting runout errors. U.S. Patent Application Publication No. 20120077329 discloses a method for obtaining a desired alignment accuracy between two functional units of a substrate during bonding and after bonding by not fixing the lower substrate. Have been described. Thereby, the lower substrate is not placed under boundary conditions and can be freely bonded to the upper substrate during the bonding process. An important feature in the known prior art is, inter alia, that a single substrate is fixed flat, usually using a vacuum device.

  The generated run-out error is usually amplified radially symmetrically about the contact location and thus increases from the contact location toward the circumferential surface. This is often a linearly increasing amplification of runout error. Under special conditions, the runout error can increase non-linearly.

Under particularly optimal conditions, the run-out error can be detected not only by means of a corresponding measuring instrument (EP 2 463 892) but also by a mathematical function. Since the runout error is translation and / or rotation and / or scaling between well-defined points, the runout error is advantageously described by a vector function. In general, such a vector function is a function f: R ² → R ² , and is therefore a mapping rule that maps a two-dimensional definition range of position coordinates to a two-dimensional value range of a “runout” vector. An exact mathematical analysis of the corresponding vector field has not yet been made, but inferences about functional properties are made. A vector function has a large probability and is at least C ⁿ n ≧ 1 and is therefore differentiable continuously at least once. Since the “runout” error increases from the contact point to the edge, the divergence of the vector function is probably different from zero. Therefore, the vector field is a spring field with a large probability.

  It is an object of the present invention to provide an apparatus and method for bonding two substrates so that the bonding accuracy, in particular the bonding accuracy at the edge of the substrate, is increased.

  This problem is solved by the features described in the characterizing portion of claim 1 and the features described in the characterizing portion of claim 9. Advantageous refinements of the invention are described in the respective claims in the form of dependent claims. All combinations of at least two features described in the specification, claims and / or drawings are also within the scope of the invention. In the stated range of values, it is desirable that values within the listed ranges themselves are considered disclosed as limit values and can be claimed in any combination.

  The idea underlying the present invention is that at least one of the two substrates, preferably the second substrate and / or the first substrate, is placed outside the bonding start position for contact surface alignment. Deformation, in particular only outside the start of the bonding, prior to bonding and / or during bonding, in particular during the progress (propagation) of the bonding wave, preferably during melt bonding. “Deformation” means in particular the initial state of the substrate, in particular a state different from the initial geometry. According to the invention, the bonding is started after the contact surface contact, in particular by dropping (separating) the first / upper substrate. The corresponding bonding means is specially defined by the configuration of the device.

  In the initial state, the substrate is often present, especially at the contact surface, possibly protruding structures (microchips, functional components) and substrate errors, eg deflection and / or thickness variations, at the contact surface. Apart from that, it is more or less flat. However, in the initial state, the substrate usually has a curvature different from zero. For 300 mm wafers, curvatures smaller than 50 μm are common. Mathematically, curvature can be viewed as a measure of the local deviation of the curve from its flat state. In a specific case, a substrate having a thickness that is small compared to the diameter is considered. Therefore, it can be called a flat surface curvature with a good approximation. In the case of a flat surface, the flat state described first is the tangential plane of the curve at the point where curvature is considered. In general, the object, in special cases, the substrate does not have a uniform curvature, so the curvature is an explicit function of position. That is, for example, a substrate that is not flat has a concave curvature at the center, but may have a convex curvature at another location. In the following, in the simplest case, curvature is always described only as “concave” or “convex” without going into the mathematical details known to mathematicians, physicists and engineers.

  A particularly unique central idea for most embodiments of the present invention is in particular: That is, the radii of curvature of the two substrates to be bonded to each other are equal or at least slightly different from each other, at least in the contact range of the substrates, that is, in the bonding front or bonding line of the bonding wave. In this case, the difference between the radii of curvature at the bonding front or bonding line of the substrate is less than 10 m, preferably less than 1 m, more preferably less than 1 cm, very preferably less than 1 mm, most preferably 0. It is smaller than 01 mm, most preferably smaller than 1 μm. In general, all embodiments of the present invention that minimize the radius of curvature R1 are advantageous. In other words, the present invention relates to a method and apparatus that allows two substrates to be bonded together so that their local alignment error, called "runout" error, is minimized. Furthermore, the underlying idea of the invention is that both substrates to be bonded to each other are controlled, in particular by a geometric, thermodynamic and / or mechanical compensation mechanism, It is to select an influencing factor for the formed bonding wave so that it does not deviate locally from each other, that is, correctly aligned. In addition, the present invention describes a product consisting of two substrates bonded together having a “runout” error reduced by the present invention.

  A characteristic feature of the present invention during bonding, particularly permanent bonding, preferably melt bonding, is the contact of the two substrates as concentric as possible. In general, contact between both substrates may be performed non-concentrically. Bonding waves propagating from non-concentric contact points reach different locations on the substrate edge at different times. Correspondingly, the complete mathematical and physical description of the bonding wave characteristics and the resulting “runout” error compensation is complicated. However, in general, the contact point is not located so far away from the center of the substrate, so that the effects that can be generated from this are negligible, at least at the edges. The distance between the possible non-concentric contact points and the center of the substrate is less than 100 mm, preferably less than 10 mm, more preferably less than 1 mm, very particularly preferably less than 0.1 mm; Most preferably, it is smaller than 0.01 mm. In the following, “contacting” generally means concentric contacting. “Center” preferably means in a broad sense the geometric center point of the underlying ideal object, preferably compensated for by asymmetry as required. That is, in an industrially widely used wafer having a notch, the center is the center point of a circle surrounding an ideal wafer having no notch. In industrially general-purpose wafers that have a flat (flat chamfered surface), the center is the center point of a circle that surrounds an ideal wafer that does not have a flat. Similar considerations apply to arbitrarily shaped substrates. However, in special configurations, it may be beneficial for “center” to mean the center of gravity of the substrate. To ensure accurate concentric point contact, the upper mounting device (substrate holder) with a central hole and a pin movable in translation in this hole is radially symmetrical. Equipped with a fixed position. It is also conceivable to use a nozzle that uses a fluid, preferably a gas, for pressurization instead of a pin. Furthermore, at least one of the two substrates, preferably the upper substrate, has a curvature imparted in the direction of the other substrate on the basis of gravity, so that in the translational approach, a corresponding second The use of such an element would be completely eliminated if a device was provided that would allow the two substrates to be brought into close proximity with each other under the other precondition of automatically contacting at sufficiently small intervals relative to the two substrates. It can be made unnecessary.

  The radially symmetric positioning is a comparable vacuum element that can fix a provided vacuum hole, circular vacuum lip or upper wafer. Use of an electrostatic mounting device is also conceivable. The pins in the central hole provided in the upper substrate holder are used for controllable bending of the fixed upper substrate.

  After the contact of the centers of the two substrates is performed, the position fixing of the upper substrate holder is released. The upper substrate falls downward due to gravity on the one hand and due to the bonding force acting between the two substrates along the bonding wave on the other hand. The upper substrate is bonded to the lower substrate in the radial direction from the center toward the side edge. In this way, the formation in the present invention of a radially symmetric bonding wave extending in particular from the center towards the side edge. During the bonding process, both substrates push the gas present between them, in particular air, from the front of the bonding wave, thereby creating a bonding interface without gas filling. The upper substrate substantially falls on a kind of gas cushion when dropped.

  The first / upper substrate is not subject to additional position fixing after the start of bonding at the bonding start location, that is, it can move freely and be distorted apart from the position fixing at the bonding start location. Any circular segment that is infinitely small with respect to its radial thickness, depending on the bonding wave that travels in the present invention, the stress conditions that occur in the bonding wave front, and the existing geometric boundary conditions. Also receives distortion. However, since the substrate is a rigid object, the strain is summed as a function of the distance from the center. This leads to a “runout” error that must be eliminated by the method according to the invention and the device according to the invention.

  The present invention therefore reduces or even completely avoids the “runout” error between two bonded substrates, especially by thermodynamic and / or mechanical compensation mechanisms. And a method and apparatus. Furthermore, the invention deals with corresponding products produced using the device according to the invention and the method according to the invention.

  In a first embodiment of the invention, the first, in particular the lower mounting device is ground to a convex or concave shape and / or polished on the mounting surface for mounting the first substrate. And / or wrapping. Preferably, since the first mounting device is ground in a convex shape, the substrate fixed to the position of the first mounting device is curved toward the contact point or the bonding start position.

  The radius of curvature of the first mount surface and / or the second mount surface is particularly greater than 0.01 m, preferably greater than 0.1 m, more preferably greater than 1 m, and even more preferably greater than 10 m. It is large, most preferably larger than 100 m, most advantageously larger than 1000 m. In a special embodiment, the radius of curvature of the first / lower mounting device is as large as the radius of curvature of the second / upper substrate formed by the actuation means, in particular by the pins, by the second / upper mounting device. In particular at least the same magnitude within the power of ten. This creates an initial position for bonding that is symmetrical with respect to the geometry.

  The first / lower mounting surface is such that the physical asymmetry is corrected by the gravitational field acting perpendicular to the mounting surface so that the bonding wavefront always moves in the same horizontal plane. It is advantageous to be ground.

  It is preferable that the first substrate and / or the second substrate are formed symmetrically in the radial direction. The substrate can have any arbitrary diameter, but the wafer diameter is particularly greater than 1 inch, 2 inches, 3 inches, 4 inches, 5 inches, 6 inches, 8 inches, 12 inches, 18 inches or 18 inches. Largely formed. The thickness of the first substrate and / or the second substrate is 1 μm to 2000 μm, preferably 10 μm to 1500 μm, more preferably 100 μm to 1000 μm.

  In particular embodiments, the substrate may have a shape that is different from a square shape or at least a circular shape. In the following, “substrate” means in particular a wafer.

In the second embodiment of the lower / first mounting device, the radius of curvature of the lower / first mounting surface is adjustable. In a particularly simple embodiment, the lower mounting device is formed thick enough to prevent it from being deformed by unintended external influence factors, but with an intended force acting from below. It has a mounting plate that is formed thin enough to be brought into a convex or concave shape. In particular, the mounting plate is greater than ^10- 7 Nm ^2, preferably greater than ^10- 3 Nm ^2, more preferably greater than 1 Nm ^2, even more preferably greater than ¹⁰ 3 Nm ^2, and most preferably Has a bending stiffness greater than 10 ⁷ Nm ² . In one embodiment of the invention, the part of the lower / first mounting device, in particular the inner part, is extendable and / or contracted pneumatically and / or hydraulically and / or piezoelectrically. It consists of a possible, preferably high-strength elastic diaphragm. In this case, the pneumatic and / or hydraulic and / or piezoelectric elements are preferably equally distributed and individually controllable.

  In yet another embodiment of the invention, the lower / first mounting device is such that the lower / first substrate is intentionally deformed by the heating means and / or cooling means before contacting, in particular Compressed or stretched in the lateral direction, and during subsequent contacting, it can be deformed as much as necessary to compensate for the "runout" error as good as possible, ideally completely. It is formed. In this embodiment, the lower / first substrate position is fixed only after the corresponding deformation, so that the thermal expansion coefficient of the lower / first substrate or the lower / first mounting device is reduced. There is no need to attach particular importance.

  In yet another special embodiment of the invention, the lower / first substrate contact is performed before the heating and / or cooling process. In order to define the (thermal) expansion of the substrate, the lower / first substrate follows the thermal expansion of the lower / first mounting device by fixing the position prior to the heating and / or cooling process, The thermal expansion coefficient of the lower / first mounting device can be used. Particularly preferably, the thermal expansion coefficient of the lower / first substrate is equal to the thermal expansion coefficient of the lower / first mounting device, so that the lower / first of the heating process and / or the cooling process is performed. There is no thermal stress on the substrate, or at least a slight thermal stress. According to the invention, it is also conceivable that the thermal expansion coefficients are different from one another. If the thermal expansion coefficients are different from each other, the lower / first substrate will on average follow the thermal expansion of the lower / first mounting device.

  In this case, the temperature difference to be adjusted between the first mounting device and the second mounting device is less than 20 ° C, preferably less than 10 ° C, more preferably less than 5 ° C, very preferably. Is less than 2 ° C, most preferably less than 1 ° C. Each mounting device is heated as uniformly as possible according to the invention. In particular, the temperature difference at any two points is less than 5 ° C., preferably less than 3 ° C., more preferably less than 1 ° C., very preferably less than 0.1 ° C. and most preferably less than 0.1 ° C. A temperature field that is smaller than 05 ° C. is provided.

  In yet another embodiment of the invention, the first mounting device may be intentionally deformed, in particular compressed and / or expanded, by mechanical actuation means at the mounting surface. Configured as follows. The first substrate fixed to the surface of the first mounting device is deformed together by deformation of the mounting device, based on its small thickness with respect to the mounting device. The deformation of the mounting device is carried out using a plurality of pneumatic and / or hydraulic and / or piezoelectric actuators, which are preferably distributed rotationally symmetrically around the substrate mount. Has been placed. For perfectly symmetric, pure radial distortion, at least three actuators are required, which are spaced 120 ° apart from each other. Preferably more than 5 actuators, more preferably more than 10 actuators, more preferably more than 20 actuators, very preferably more than 30 actuators, most preferably more than 50 actuators are used Is done.

  In yet another embodiment of the present invention, the contact surfaces of both substrates are bonded together in a vertical orientation. The role of this particular embodiment is inter alia: That is, to reduce the deformation of the wafer due to gravity, preferably at least symmetrically, particularly preferably to completely prevent and / or compensate for deformation due to gravity. Preferably, in the vertical position, both substrates are curved toward the bonding start location by means of each one actuating means, in particular each pin, in particular simultaneously and symmetrically with respect to the bonding start location. The convex surface at the starting point can be contacted. A particularly automatic bonding process with a bonding wave is started by separating at least one of the two substrates from the mounting surface.

  Embodiments in the present invention are preferably operated in a defined and particularly controllable atmosphere, in particular under normal pressure.

All embodiments of the invention described above are carried out in a special variant embodiment in a low vacuum, more preferably in a high vacuum, even more preferably in an ultra-high vacuum, in particular less than 100 mbar. At a low pressure, preferably below 10 ^-1 mbar, more preferably below 10 ^-3 mbar, more preferably below 10 ^-5 mbar, most preferably below 10 ^-8 mbar. To be implemented.

  In yet another embodiment of the invention, at least one influencing factor on the propagation of the bonding wave, in particular the propagation speed and / or at least one influencing factor on the orientation of the contact surface is controlled. The bonding wave is controlled particularly with respect to its speed. The control of the speed takes place in particular indirectly via the composition and / or density and / or temperature of the gas in the atmosphere in which the bonding takes place. The method according to the invention should preferably be carried out in a low-pressure atmosphere, preferably in a vacuum, but it is advantageous to carry out the bonding process in another atmosphere, in particular in the region of normal pressure. obtain. Due to the point contacts, the bonding wave always proceeds radially symmetrically from the center toward the side edge during bonding in the present invention, and in this process, the annular gas cushion is pushed ahead of the bonding wave itself. Along the bonding wave, in particular along a substantially annular bonding line (bonding front), a bonding force is so great that no gas bubble inclusions can be generated. Therefore, the upper / second substrate is placed on a kind of gas cushion during the bonding process.

  The selection of the gas / gas mixture in the present invention and the definition of the properties of the gas cushion set how quickly and how strongly the second substrate can be lowered and / or extended. Furthermore, the speed of the bonding wave can also be controlled via the gas properties.

According to yet another, particularly independent configuration of the present invention, the composition of the gas mixture is selected. Preferably, a gas having the smallest possible type of atoms and / or molecules with a correspondingly low inertia at a given temperature is used. Therefore, the molar mass of at least one gas component of the gas components is less than 1000 g / mol, preferably less than 100 g / mol, more preferably less than 10 g / mol, very particularly preferably 1 g / mol. Smaller than. More preferably, the density of the gas mixture used is adjusted in particular as small as possible and / or the temperature is adjusted in particular to the required height. According to the invention, the gas density is less than 10 kg / m ³ , preferably less than 1 kg / m ³ , more preferably less than 0.1 kg / m ³ , very particularly preferably from 0.01 kg / m ³ . Is also adjusted small. According to the invention, the temperature of the gas is higher than 0 ° C., preferably higher than 100 ° C., more preferably higher than 200 ° C., very preferably higher than 300 ° C., most preferably higher than 400 ° C. Highly adjusted. According to the invention, the parameters listed above are selected such that the selected gas mixture or the individual components of the gas mixture do not condense. This avoids liquid encapsulation on the surface of the substrate during the bonding process.

  Similar ideas apply to gas mixtures whose thermodynamic properties are depicted in multi-component phase diagrams. Changes in the composition and / or pressure and / or temperature of the gas mixture affect the motion characteristics of the first substrate and / or the second substrate, thereby reducing “runout” errors.

  Particularly preferably, all variable parameters are set so that the bonding wave propagates at the optimum speed possible with respect to the existing initial and boundary conditions. In particular in the atmosphere present, especially at atmospheric pressure, the slowest possible speed of the bonding wave is advantageous. The speed of the bonding wave is in this case lower than 200 cm / s, preferably lower than 100 cm / s, more preferably lower than 50 cm / s, very preferably lower than 10 cm / s, most preferably 1 cm / s. Lower than. In particular, the speed of the bonding wave is higher than 0.1 cm / s. In particular, the speed of the bonding wave is constant along the bonding front. In a vacuum atmosphere, the speed of the bonding wave is automatically increased. This is because the substrate bonded along the bonding line does not have to overcome the resistance caused by the gas.

  In yet another particularly independent configuration of the invention, in the upper / second mounting device, a stiffening plate is fitted between the mounting surface and the upper / second substrate. The stiffening plate is bonded, particularly temporarily, to the substrate to change the properties of the upper / second substrate during bonding. The connection between the stiffening plate and the upper / second substrate is made by a structural technical fixation in the stiffening plate. Such fixation is preferably vacuum fixation. Electrostatic fixing, ultra-thin mechanical fixing that surrounds and tightens the substrate at the edge, and adhesive fixing with a highly polished stiffening plate surface are also conceivable.

  In yet another, particularly independent configuration of the present invention, the “runout” error is adjusted by a very small spacing between the two substrates before contact and / or outside the bond start location. This spacing is in particular smaller than 100 μm, preferably smaller than 50 μm, more preferably smaller than 20 μm, very particularly preferably smaller than 10 μm.

  According to the invention, it is particularly advantageous if the radii of curvature of the two substrates differ from one another by less than 5%, preferably at the bonding front, preferably equal to one another.

  In another special refinement of all embodiments of the present invention, the lower / first mounting device and / or the upper / second mounting device have actuating means, in particular with central holes and pins. Thus, by using these operating means, it is possible to generate a convex curve of each substrate in the direction of the bonding start location.

  The control of the steps and / or movements and / or sequences described above, in particular the control of the pins for bending the substrate, the mutual access of the substrates, the temperature control, the pressure control and the gas composition control are preferably a central control unit, in particular This is done via a computer with control software.

  The mounting and positioning of the substrate in the mounting device can be performed in any possible manner and using any known technique. According to the invention, in particular, a sample holder with a vacuum sample holder, an electrostatic sample holder, a mechanical clamp is conceivable. In order to allow the substrate sufficient flexibility and freedom of expansion and contraction within the position fixing part, it is preferred that the board is fixed only along the circular segment located as large as possible in the region of the side edge. .

  Yet another particularly independent configuration of the present invention is to perform contacting in as coordinated manner as possible and at the same time automatically. In this case, at least one of the two substrates is preloaded (preload) extending concentrically radially outward with respect to the center M of the contact surface of the substrate before contact. Loaded, and then only affects the start of contacting, and after a given section, especially after contact of the center M of the board, the board is released and automatically controlled based on its preload. And bonded to the other substrate. Preloading is achieved by deforming the first substrate by deformation means. In this case, the deformation means act on the side opposite to the bonding side, in particular on the basis of its shape, and correspondingly the deformation can be controlled by the use of different (especially interchangeable) deformation means. The control is also performed by the force when the pressure or the deformation means acts on the substrate. In this case, it is advantageous to reduce the effective mounting surface of the mounting device provided with the semiconductor substrate, so that the semiconductor substrate is only partially supported by the mounting device. In this way, a smaller contact surface provides a reduced adhesion between the wafer and the sample holder or mounting device. According to the present invention, the position fixing portion is applied only in the range of the peripheral surface of the semiconductor substrate (first substrate). The smallest possible mounting surface between the semiconductor substrates is provided. Therefore, the semiconductor substrate can be peeled gently and reliably at the same time. This is because the peeling force necessary for peeling the wafer is formed as small as possible. Peeling is particularly controllable, especially by reducing the negative pressure on the mounting surface. “Controllable” means that after contact between the first wafer and the second wafer, the first wafer is still fixed in position on the sample holder, and the negative pressure on the mounting surface is intentionally (controlled) This means that the substrate (wafer) is peeled off from the sample holder (mounting device) only from the inside, particularly from the inside to the outside. The above embodiment of the present invention allows in particular peeling to be performed with very little force.

  The substrates (wafers) are aligned with respect to each other before the bonding process, so that the overlap of the corresponding structures on the substrate surface (exact alignment, in particular with an accuracy of less than 2 μm, preferably less than 250 nm) More preferably, an alignment with an accuracy of less than 150 nm, most preferably with an accuracy of less than 100 nm) is ensured. In the bonding method according to the present invention, the wafers are not overlapped flat, but are first brought into contact with each other at the center M. In this case, one of the wafers is slightly pressed against the second wafer. Or correspondingly deformed in the direction of the opposite wafer. After the deformed and bent wafers (in the direction of the wafers facing each other) are released, the bonding wave progresses with minimal force and thus with minimal horizontal distortion mainly. In particular, continuous and uniform welding along the bonding front takes place, at least almost completely automatically.

  Yet another particularly independent configuration of the invention is to control the deformation of the first substrate and / or the second substrate in relation to a defined influence factor on the progress of the bonding wave. These factors include, among other things, the ambient pressure surrounding the substrate, the type of gas / gas mixture present in the atmosphere, the temperature, the distance between the substrates outside the bond start location, the bonding strength of the substrate, and in some cases Include pre-treatment steps present, surface properties, surface roughness, material at the surface as well as wafer thickness / bending stiffness.

  When the bonding start location is arranged at the center of the contact surface of the substrate, it is possible to achieve uniform (particularly concentric) progress (propagation) of the bonding wave.

  It is particularly advantageous if the deformation of the first substrate and / or the second substrate is performed laterally and / or convexly and / or concavely, more preferably mirror-symmetrically. In other words, the deformation is effected according to the invention, in particular by stretching or compressing or bending the first substrate and / or the second substrate.

  Preferably, the substrates have approximately the same diameter D1, D2. The diameters D1, D2 differ from one another, in particular by less than 5 mm, preferably by less than 3 mm, more preferably by less than 1 mm.

  In a further, particularly independent configuration of the invention, the deformation is effected by mechanical actuation means and / or temperature control of the first and / or second mounting device.

  Since the first substrate and / or the second substrate are fixed to the first mounting surface and / or the second mounting surface only in the range of the side wall, the deformation in the present invention can be realized more easily. Become.

  Features relating to the disclosed apparatus also apply to features relating to the method, and characteristics relating to the disclosed method also apply to features relating to the apparatus.

  Further advantages, features and details of the invention will become apparent from the embodiments described below with reference to the drawings.

1 is a schematic cross-sectional view showing a first embodiment of an apparatus according to the present invention. FIG. 4 is a schematic cross-sectional view showing a second embodiment of the device according to the invention. FIG. 6 is a schematic cross-sectional view showing a third embodiment of the device according to the invention. FIG. 6 is a schematic cross-sectional view showing a fourth embodiment of the apparatus according to the present invention. FIG. 7 is a schematic cross-sectional view showing a fifth embodiment of the apparatus according to the present invention. It is the schematic which shows the method step of the bonding in this invention. FIG. 3 is a schematic diagram showing a bonded substrate pair having an alignment error dx in the range of the side edges of the substrate. It is an enlarged view of two substrates in the range of the bonding wave in the present invention. It is an enlarged view of two substrates without alignment error / runout error. FIG. 4 is an enlarged view of two substrates having alignment error / runout error. FIG. 5 is a schematic diagram symbolically showing possible overlay errors or “runout” errors.

  In the drawings, the same components and components having the same functions are denoted by the same reference numerals.

  FIG. 1 shows a lower first mounting apparatus 1 as a substrate sample holder. The lower first mounting apparatus 1 includes a base 9 and a mount body 2. The mount body 2 has a first mount surface 2o arranged in the direction of the second mount device 4 that is located facing upward. The first mount surface 2o is curved in a convex shape in the illustrated example. The mount body 2 is formed to be replaceable as a module and can be separated from the base body 9. Therefore, the base body 9 is used as an adapter between the mount body 2 and a lower mount unit of a bonder (not shown). Thereby, according to this invention, it becomes possible to implement quick exchange between the various modular mount bodies 2 which have mutually different curvature radii R as needed.

  A fixing means 6 in the form of a vacuum path is arranged on the mount body 2. By this fixing means 6, the position of the lower first substrate 3 can be fixed to the mount surface 2o.

  The radius of curvature R is preferably very large according to the present invention, and as a result, the curvature is actually not visually recognizable (shown in a highly exaggerated manner in the drawing). Therefore, it can be considered that the first mounting device is configured without the fixing means 6 and the first substrate is simply placed on the mounting surface 2o. According to the invention, attachment by electrostatic, electrical or magnetic fastening means is also conceivable.

  The second mounting device 4 formed as a substrate sample holder has a base 2 ′. The base body 2 'is provided with a second mounting surface 2o', which in particular in a concentric section, etc., with respect to the corresponding concentric section of the first mounting surface 2o, etc. It can be aligned to the interval.

  The base body 2 ′ has an opening 5 in the form of a hole and a fixing means 6 ′ similar to the fixing means of the first mounting device 1.

  The fixing means 6 'is used to fix the position of the upper second substrate 8 on the side opposite to the contact surface 8k.

  Actuating means in the form of pins 7 are used for deforming (in this case bending) the second substrate 8, and in particular the second substrate 8 of the curved first substrate 3, In particular, it is used to bring the maximum curvature into a point shape.

  In a special configuration according to the invention, the mount body 2 can be extended, pneumatically (aerodynamic) and / or hydraulically (hydraulic) inflatable / shrinkable components, in particular cushions, in particular heat resistant and It is conceivable to form a cushion made of a material having corrosion resistance.

  FIG. 2 shows a second embodiment having a mount body 2 ″. In the mount body 2 ″, the first mount surface 2o can be controlled and deformed by the actuating element 10 formed as a tension rod and / or a pressing rod. The mount body 2 ″ has an annular fixed section 16 that extends concentrically over the entire circumference, and a deformation section 17 that includes the first mounting surface 2o. This deformation section 17 has at least a substantially constant thickness and thus a substantially constant bending stiffness. The actuating element 10 is arranged on the actuating side of the deformation section 17 opposite to the first mounting surface 2o and is particularly fixed in position. By means of the actuating element 10, the deformation section 17 can be deformed in the micrometer range, in particular it can be curved in an uneven surface. The actuating element 10 in this case is greater than 0.01 μm, preferably greater than +/− 1 μm, more preferably greater than +/− 10 μm, very particularly preferably greater than +/− 100 μm, most preferably + It moves greater than / -1 mm, most advantageously greater than +/- 10 mm. In other respects, the embodiment shown in FIG. 2 corresponds to the embodiment shown in FIG.

  FIG. 3 shows a third embodiment of the first mounting apparatus 1 provided with a mount body 2 ″ ″. The mount body 2 ″ ″ has a first mount surface 2 o for mounting the first substrate 3. Further, in the present embodiment, the first mounting apparatus 1 is configured to control the temperature (heating and / or heating) of the mount body 2 ″ ″ at least in the range of the first mount surface 2o, preferably in the entire range of the mount body 2 ″ ″. Temperature control means 11 for cooling).

  In the first method, the position of the first substrate 3 is fixed to the heated mount body 2 "" only after the expansion and contraction generated based on the temperature difference is achieved. Thereby, the 1st board | substrate 3 is expanded-contracted according to the intrinsic | native thermal expansion coefficient.

  In the second method, the position of the first substrate 3 is fixed to the mount body 2 ″ ″ before a thermal load is applied by the temperature control means 11. Due to the change of the temperature control means 11, the mount body 2 ″, and hence the first mount surface 2 o, along with the first substrate 3 fixed to the first mount surface 2 o, particularly extends in the lateral direction. Preferably, the mount body 2 ″ ″ has substantially the same thermal expansion coefficient as that of the first substrate 3. In other respects, the third embodiment corresponds to the first embodiment and the second embodiment described above.

FIG. 4 shows a fourth embodiment having a base body 9 ′ with a receiving section 18 for receiving the mount body 2 ^IV . Furthermore, the base body 9 ′ has a shoulder section 19, which is formed in an annular shape, following the receiving section 18. This shoulder section 19 serves as a stop for the actuating element 12 used to deform the mount body 2 ^IV laterally. The actuating elements 12 are distributed and arranged on the lateral peripheral surface of the mount body 2 ^IV , in particular as a number of tension elements and / or pressing elements 12. The actuating element 12 is used to deform the mounting body 2 ^IV in the lateral direction, in particular by mechanical extension and / or compression, preferably in the micrometer range. The mount 2 ^IV is in this case larger than 0.01 μm, preferably larger than +/− 1 μm, more preferably larger than +/− 10 μm, very particularly preferably larger than +/− 100 μm, most preferably It is stretched / compressed greater than +/− 1 mm, most advantageously greater than +/− 10 mm. The actuating element 12 may be formed as a purely mechanical and / or pneumatic and / or hydraulic and / or piezoelectric component.

In other respects, the fourth embodiment corresponds to the first embodiment, the second embodiment, and the third embodiment described above. Particularly important in the fourth embodiment is that the bonding portion between the substrate 1 and the mount body 2 ^IV is extremely large, and the substrate 1 is used to stretch or compress the mount body 2 ^IV by the operating element 12. In the meantime, it is also stretched or compressed accordingly.

FIG. 5 shows a fifth embodiment. In the fifth embodiment, the first mounting device 1 and the second mounting device 4 are oriented in the vertical direction. First mounting device 1 includes a substrate 9'', and a mount member 2 ^V, which is positioned and fixed by the base 9''. Mounting member 2 ^V is, in the present embodiment has a first mounting surface 2o arranged vertically, the first substrate 3 is fixed in position via the fixing means 6 to the first mounting surface 2o .

Second mounting device 4 for receive and position fixing the mounting body 2 ^IV, having arranged substrate 9''' to be positioned opposite. The mount body 2 ^IV is used for mounting and fixing the position of the second substrate 8 on the mount surface 2 o ′ arranged in the vertical direction. In order to deform the second substrate 8, an opening 5 similar to the opening 5 shown in FIG. 1 is provided, this opening 5 being provided with actuating means in the form of pins 7. The pin 7 is formed so as to deform the second substrate 8 through the opening 5. In this case, the pin 7 deforms the side opposite to the contact surface 8 k of the second substrate 8. The pin 7 defines the bonding start point 20 when the two substrates 3 and 8 are contacted due to the deformation of the second substrate 8.

  Apart from the opening 5 and the pin 7, the first mounting device 1 and the second mounting device 4 are formed symmetrically in the fifth embodiment shown in FIG. Preferably, the first mounting device 1 also has a corresponding opening and a corresponding pin, so that a symmetrical deformation of both substrates 3 and 8 is possible. In particular, after the deformed substrates 3 and 8 are contacted at the bonding start point 20 arranged at the center of both the substrates 3 and 8, both the fixing means 6 and 6 'are dissociated at the same time. Since 8 behaves the same, no alignment error will occur during the advancement of the bonding wave, even if there is no gravity effect on the deformation of the contact surfaces 3k, 8k in the approaching direction. This is especially true when the overwhelming number of influence factors in the present invention on the bonding wave or alignment error, particularly when the substrate thickness or substrate bending stiffness is the same. Bending stiffness is the resistance of an object to bending that is forced on the object. The higher the bending stiffness, the greater the bending moment must be formed in order to obtain the same curvature.

  Bending stiffness is a pure material and shape-dependent quantity that is independent of bending moment (assuming that the bending moment does not change the moment of inertia or the secondary moment of inertia due to cross-sectional changes). The cross section at the center of the wafer is a very good approximation, a square cross section having a thickness t3 and a wafer diameter D. Bending stiffness is the product of the modulus of elasticity and the moment of inertia for a uniform cross section. The cross-sectional second moment of a square cross section about an axis perpendicular to the thickness is directly proportional to the cube of the thickness. That is, the moment of inertia, and hence the moment of inertia of the cross section, is influenced by the thickness. The bending moment is caused by the action of gravity along the substrate. That is, if the bending moment is constant and thus the gravity is constant, the substrate having a large thickness is bent slightly more than the substrate having a small thickness based on the large second moment of section.

  FIG. 6 schematically shows the bonding process. In this case, the radius of curvature R of the first mounting device 1 is drawn greatly exaggerated for easy understanding of the drawing. According to the present invention, this radius of curvature is several meters when the diameter of the substrates 3 and 8 is in the range of 1 inch to 18 inches and the thickness of the substrates 3 and 8 is in the range of 1 μm to 2,000 μm. It becomes.

  The substrates 3 and 8 are contacted with the contact surfaces 3k and 8k in the range of the bonding start location 20 located in the center of the substrates 3 and 8, and the second substrate 8 is released from the second mounting device 4 ( After dissociation), bonding starts. The bonding wave having the bonding front 13 extends concentrically from the bonding start point 20 to the side edges 8 s and 3 s of the substrates 3 and 8.

  At this time, the bonding wave pushes out the gas 15 (or the gas mixture 15) indicated by an arrow between the contact surfaces 3k and 8k.

  According to the present invention, the first substrate 3 is deformed by the mounting device 1 so that the alignment errors of the corresponding structures 14 of both substrates 3 and 8 are minimized.

  The second substrate 8 is deformed based on the acting force during the propagation of the bonding wave (after the start of bonding and the dissociation from the mounting device 4). The acting force is gas pressure, gas density, bonding wave speed, gravity, and natural frequency (spring characteristic) of the second substrate 8.

  In particular, in the illustrated embodiment corresponding to the first two embodiments shown in FIGS. 1 and 2, the deformation is effected by the curvature of both substrates 3, 8. In this case, the radius of curvature R of the upper substrate 8 corresponds to the radius of curvature R1 of the lower substrate 3, particularly at any point in the bonding front 13. If either one of the mounting surfaces 2o, 2o ′ is flat, and accordingly the radius of the corresponding substrate 3 or 8 supported on the flat mounting surface 2o or 2o ′ is also infinite, The radius of the substrate 8 or substrate 3 located on the opposite side is also adjusted to a corresponding size, and in an extreme case it is adjusted to infinity. Accordingly, the present invention also compensates for “runout” errors by bringing two substrates 3, 8 having infinite radii of curvature, ie, two substrates 3, 8 having contact surfaces 3k, 8k parallel to each other. Is done. Such a special case in the present invention is particularly suitable in a vacuum enclosure for bonding both substrates 3, 8 together. This is because it is not necessary to bond the substrates 3 and 8 to each other by a bonding wave that propagates from the bonding center and pushes the gas amount forward from the bonding interface. According to the invention, the difference between the curvature radii R1, R is especially less than 100 m, preferably less than 10 m, more preferably less than 1 m, very preferably less than 1 cm, very particularly preferably from 1 mm. Is also formed small.

  In this case, according to the present invention, it is conceivable to control the environment and the bonding speed by selecting the gas 15 or the gas mixture 15 and setting the pressure and / or temperature.

  As shown in an enlarged form in FIGS. 7a-7d, the possibly occurring alignment error dx shown in FIGS. 7a and 7d is shown in FIGS. 7b and 7c according to the present invention. As described above, at least most of the substrates 3 and 8 are removed by deforming the substrates 3 and 8.

  The previously described method steps, in particular the movements and parameters, are controlled in particular by a software assisted control device (not shown).

1 first mounting device ^{2,2', 2'', 2''', 2 IV} , 2 V, 2 V1 mounting body 2o first mounting surface 2o' second mount surface 3 first substrate 3k first 1 contact surface 3s side edge 4 second mounting device 5 opening 6, 6 ′ fixing means 7 pin 8 second substrate 8k second contact surface 8s side edge 9, 9 ′, 9 ″, 9 ′ ″ ″ Base 10 Actuating element 11 Temperature control means 12 Actuating element 13 Bonding front 14, 14 ′ Structure 15 Gas / gas mixture 16 Fixed section 17 Deformation section 18 Containment section 19 Shoulder section 20 Bonding start location dx Positioning error d1, d2 Diameter R, R1 radius of curvature

Claims (13)

A method of bonding a first substrate (3) to a second substrate (8) at the contact surfaces (3k, 8k) of both substrates (3, 8), comprising the following steps, in particular the following sequence:
The first substrate (3) is mounted on the first mounting surface (2o) provided in the first mounting device (1), and the second substrate (8) is mounted on the second mounting device (4). Mounting on a second mounting surface (2o ′) provided on
Contacting the contact surfaces (3k, 8k) at a predetermined bonding start point (20);
The first substrate (3) is connected to the second substrate (8) along the bonding wave that travels from the bonding start point (20) to the side edges (3s, 8s) of both substrates (3, 8). Bonding, and
In a method comprising:
The first substrate (3) and / or the second substrate (8) is bonded to the contact surface (3k, 8k) before bonding and / or bonding outside the bonding start point (20) for the alignment of the contact surfaces (3k, 8k). A method of bonding substrates, wherein the substrate is deformed during the process.   2. The method according to claim 1, wherein the deformation of the first substrate (3) and / or the second substrate (8) is carried out in relation to a defined influencing factor that influences the progress of the bonding wave.   The method according to claim 1 or 2, wherein the bonding start point (20) is arranged at a central portion of the contact surface (3k, 8k).   4. The method as claimed in claim 1, wherein the deformation of the first substrate (3) and / or the second substrate (8) is carried out laterally and / or concavely or convexly.   5. The method according to claim 1, wherein the deformation is performed by stretching or compressing or bending the first substrate (3) and / or the second substrate (8).   The diameters (d1, d2) of the two substrates (3, 8) differ from each other by less than 5 mm, in particular by less than 3 mm, preferably by less than 1 mm. The method of any one of these.   The deformation according to any one of claims 1 to 6, wherein the deformation is performed by mechanical actuation means and / or by temperature control of the first mounting device (1) and / or the second mounting device (4). The method according to claim 1.   The first mount surface (2o) and / or the second mount surface is arranged only in the range of the side edge portions (3s, 8s) with respect to the first substrate (3) and / or the second substrate (8). The method according to claim 1, wherein the position is fixed at (2o ′). An apparatus for bonding a first substrate (3) to a second substrate (8) at the contact surfaces (3k, 8k) of both substrates (3, 8):
A first mounting device (1) for mounting the first substrate (3) on the first mounting surface (2o) and a second mounting device for mounting the second substrate (8) on the second mounting surface (2o '). Two mounting devices (4);
Contact means for contacting the contact surfaces (3k, 8k) at a predetermined bonding start point (20);
In an apparatus for bonding substrates, comprising:
The first substrate (3) and / or the second substrate (8) is bonded to the contact surface (3k, 8k) before bonding and / or bonding outside the bonding start point (20) for the alignment of the contact surfaces (3k, 8k). An apparatus for bonding substrates, wherein a deformation means for deforming the substrate is provided.   10. The device according to claim 9, wherein the deformation means comprise the first mounting device (1) deformable laterally and / or convexly or concavely, in particular at the first mounting surface (2o). .   10. The second mounting device (4) according to claim 9, wherein the deformation means comprise the second mounting device (4) deformable laterally and / or convexly or concavely, in particular at the second mounting surface (2o '). apparatus.   The deformation means comprises mechanical actuating means and / or temperature control means for controlling the temperature of the first mounting device (1) and / or the second mounting device (4). Item 12. The device according to any one of Items 9 to 11.   The first mount surface (2o) and / or the second mount surface is arranged only in the range of the side edge portions (3s, 8s) with respect to the first substrate (3) and / or the second substrate (8). The device according to any one of claims 9 to 12, wherein a position fixing means for fixing the position at (2o ') is arranged.

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